Abstract node side functionality of attachable plugins

- Expand Attacher/Detacher interfaces to break up work more
  explicitly.
- Add arguments to all functions to avoid having implementers store
  the data needed for operations.
- Expand unit tests to check that Attach, Detach, WaitForAttach,
  WaitForDetach, MountDevice, and UnmountDevice get call where
  appropriet.

test/integration/persistent_volumes_test.go

@@ -54,7 +54,7 @@ func TestPersistentVolumeRecycler(t *testing.T) {
 	testClient := clientset.NewForConfigOrDie(&restclient.Config{Host: s.URL, ContentConfig: restclient.ContentConfig{GroupVersion: testapi.Default.GroupVersion()}, QPS: 1000, Burst: 100000})
 	host := volumetest.NewFakeVolumeHost("/tmp/fake", nil, nil)
 
-	plugins := []volume.VolumePlugin{&volumetest.FakeVolumePlugin{"plugin-name", host, volume.VolumeConfig{}, volume.VolumeOptions{}, 0, 0}}
+	plugins := []volume.VolumePlugin{&volumetest.FakeVolumePlugin{"plugin-name", host, volume.VolumeConfig{}, volume.VolumeOptions{}, 0, 0, nil, nil, nil, nil}}
 	cloud := &fake_cloud.FakeCloud{}
 
 	binder := persistentvolumecontroller.NewPersistentVolumeClaimBinder(binderClient, 10*time.Second)